A synthetic-resin article is usually cast in a mold constituted of a pair of mold halves together forming a mold cavity. A liquid synthetic-resin mass is injected into this cavity and is hardened therein. Thereupon the two mold halves are separated and ejector or knockout rods fitted in one of the mold halves are advanced so as to free the molded article from the mold. Typically one of the mold halves is substantially more intricately shaped than the other so that the molded article on separation of the two mold halves can be relied on to remain in this half, which is also usually the lower mold half and which is provided with the ejector rod or rods.
Between each molding operation it is frequently the practice to spray the interior of the mold with a release agent or similar treatment fluid. This is usually carried out by the operator of the molding device who manually sprays the interior by means of a spray head carried on a hose connected to a source of fluid. This spray head is directed at the surfaces to be treated while a valve is actuated to propel the fluid with gas pressure from the end of the head.
Such an arrangement has the considerable disadvantage that it requires the operator visually to gauge just how much of the treatment fluid is applied. In addition the operator must usually place his hand between the mold halves, creating the possibility of serious injury to him.
It has also been suggested to provide automatic devices which swing in between the separated mold halves after ejection of the molded article and automatically spray a dosed quantity of treatment liquid into the mold cavity. Such arrangements are relatively complicated and quite expensive. Also they rarely supply a sufficient amount of treatment liquid to the upper mold half. Such automatic devices are necessary however when the treatment fluid includes a noxious element, as is particularly the case with polytetrafluoroethylene emulsions, lacquers, posttreatment agents, and pretreatment agents.